apple gift card redeemed but not by me, how do I contact corporate office?

this link has the information you need - If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card - Apple Support

There's a scam where thieves can read the numbers of a card in a store and then wait until somebody buys the card. It gets activated at the register and then the thieves try to redeem the card before you do. Always redeem cards as soon as possible after you buy them. I step away from the register and redeem my phone cards about 30 seconds after buying them. Also check cards for any sign of tampering.

By all means read the document referred to in a previous post. It tells you how to contact Apple but for a place to actually write a letter:

Contacting Apple - https://www.apple.com/contact/

Read the links below about various ways to pay for items in the iTunes and App Stores.

- Add a payment method such as a credit or debit card to your account. See this link about 'Payment methods that you can use with your Apple ID' --> https://support.apple.com/HT202631 then see this link about how to 'Change, add, or remove Apple ID payment methods' --> https://support.apple.com/HT201266

- Add money to your Apple ID balance - "Use a payment method, such as a credit or debit card, to add funds to your Apple ID balance." This takes the previous payment method one step farther by optionally using it to irreversibly add balance to an Apple ID instead of having the card charged each time.

Click here --> https://support.apple.com/HT208687

- Create and add money to an iTunes Pass - "At Apple Stores and select retailers, you can add store credit directly to the Apple ID that you use for App Store, iTunes Store, and iBooks Store purchases." - https://support.apple.com/HT203021

- Redeem your App Store & iTunes Gift Card --> https://support.apple.com/HT201209

Well, maybe you're not so inclined to use the last one now. ;-D